The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Recently, a roof antenna for receiving DMB (Digital Multimedia Broadcasting) broadcasting or the like has been installed on a roof panel of a vehicle.
A typical roof antenna is fixed by a fastening means such as a bolt or a nut, and a fastening portion of the roof antenna enters a mounting hole which is formed at the roof panel of the vehicle. Since the roof antenna is installed in a moving vehicle, it needs to be firmly connected to the roof panel. In addition, the watertightness of the mounting portion is desired to prevent the inflow of rainwater through the mounting hole of the roof panel.
It is not preferable that the fastening force of the fastening means is excessively large or small to mount the roof antenna on the roof panel. If the fastening force is too large, it may cause deformation of the roof panel, and if the fastening force is too small, the watertight performance of the mounting portion may be deteriorated.